Rolling bearing and method for the production thereof

ABSTRACT

A bearing ring comprises a raceway for a rolling member as well as at least one lateral rim for axially guiding the rolling member. To produce the bearing ring a notch is introduced into a running surface of the bearing ring which faces the rolling member. A final contour of the bearing ring is created by means of a hard turning process.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Divisional Application of U.S. patentapplication Ser. No. 12/158,391, filed Jun. 20, 2008, which is a 371 ofInternational application PCT/DE2006/002193, filed Dec. 9, 2006, whichclaims priority of DE 10 2005 061 179.6, filed Dec. 21, 2005, thepriority of these applications is hereby claimed and these applicationsare incorporated herein by reference.

DESCRIPTION

1. Field of the Invention

The present invention relates to a roller bearing and a method for theproduction thereof. In particular, the invention relates to a method forproducing a bearing ring of the roller bearing and an associated rollerbody.

2. Background of the Invention

Various roller bearings are known from the prior art. For example,roller bearings are known in which a bearing ring, i.e. the outer ringand/or the inner ring, has a rim in order to absorb axial forces actingon the bearing. In methods for producing roller bearings which are knownfrom the prior art, the respective bearing rings are produced by meansof a turning method and subsequently what is referred to as a grindingundercut is provided in a still unhardened state in a corner regionbetween the raceway of the bearing ring and the lateral rim. Thisgrinding undercut is required to be able to subsequently grind theraceway and the rim running face.

This grinding undercut results in a sharp edge in the rim running face.This edge, in turn, in combination with unsuitable lubricants, candamage roller end faces due to the axial running on of the roller endfaces. To be more precise, due to the edge it is possible for minordamage to occur to the roller bodies and their end faces. In particularwhen roller bodies are used with planar roller end faces, such damage tothese faces by the edge is likely to occur.

SUMMARY OF THE INVENTION

The present invention is based on the object of making available amethod for producing a roller bearing with which a roller bearing can bemade available with a prolonged service life compared to the prior art.In addition, the intention is to increase the axial load-bearingcapacity of bearings.

The present invention is also aimed at a roller bearing which achievesimproved contact between the end faces of the roller bodies on the onehand and the inner wall of the rim on the other.

The aforesaid objects are achieved by means of the subject matters ofthe independent claims. Advantageous embodiments and developments arethe subject matter of the subclaims. However, it is to be noted that thesubject matters of all the subclaims do not solve all the inventiveproblems to the same degree.

Furthermore, it is to be noted that the subject matters of all theindependent claims are based on the same problem, namely of increasingthe service life of the roller bearings.

In the inventive method for producing a bearing ring for a rollerbearing, wherein the bearing ring has a raceway for a roller body and atleast one lateral rim for axially guiding the roller body, in one methodstep a notch is made in a wall of the bearing ring facing the rollerbody. According to the invention, the end contour of the bearing ring isproduced by a hard turning process.

The rim is preferably also used for absorbing loads acting axially onthe roller bearing.

An end contour of the bearing ring is understood to be a contour whichonly still requires fine processing for completion, the formation of thenotch also being considered to be fine processing.

The bearing ring which is already hardened is processed by means of thehard turning process according to the invention. In this case, there isno need to grind the rim running face further.

A notch is understood to be a groove or recess which is preferablyformed essentially in the radial direction in the bearing ring. Thisnotch, which performs the function of a grinding undercut, is preferablylocated in a corner region between the rim running face and the raceway.

The present invention is also aimed at a method for producing a bearingring for a roller bearing, wherein the bearing ring has a raceway for aroller body and at least one lateral rim for axially guiding the rollerbody. In this context, in one method step, a notch is made in a wall ofthe bearing ring facing the roller body. According to the invention, inthis method the notch is produced by forming a groove with a groove bodyin essentially the radial direction of the roller bearing.

The groove body can be used to form a groove in the radial direction ofthe roller bearing if the lateral rim or its inner wall no longer needsto be subsequently ground. Forming a groove with the groove body in theradial direction of the roller bearing prevents an edge being producedin the rim running face and damaging the individual roller bodies duringlater operation.

In a further method step the raceway is preferably ground. The notch inthe corner region between the raceway and the lateral rim is used tocarry out this grinding. The notch prevents damage to the rim face bythe grinding tool. In a further preferred embodiment, the rim is hardturned with a rim angle of aperture of more than 90°. After this hardturning, in a last work step the notch or the grinding undercut isformed in order to permit the raceway to be ground.

The rim angle of aperture is preferably between 90° and 92°. The contactgeometry between the roller body and the rim running face is improved bythis rim angle of aperture.

To be more precise, the run up between the roller bodies and the rim isimproved by this rim angle of aperture which is slightly above 90°, forexample 90.5°, therefore increasing the service life of the rollerbearing.

The present invention is, as stated above, also aimed at a method forproducing a roller body for a roller bearing, wherein the roller bodyhas at least one end face which is curved in sections. As stated above,planar end faces, which are subject to high stresses when in contactwith the rim, are used in the prior art. Provision of a curved end faceensures that instead of a contact face, known from the prior art,between the roller and the rim, only essentially a point of contactoccurs between the roller body and the rim. The lubrication between theroller body and the rim can also be improved.

In this way, the service life and the axial load-bearing capacity of thebearing according to the invention can also be increased. The end faceof the roller body is understood to be that face which is turned towardsthe rim. According to the invention, the roller body is also produced bymeans of a hard turning process. Using a hard turning processfacilitates the production of a curved end face according to theinvention.

The end face is preferably curved at least in sections, in particular iscurved logarithmically or in a toroidal shape.

A toroidal body is understood to be a body which is produced as a resultof the turning of a circle about an axis lying in the circular planeoutside the circle. With respect to the roller body, a toroidal end faceis understood to mean that the end face produces a line in a projectionin a radial direction of the roller body, and this line is curved inparticular in a circular or ellipsoidal shape in its end regions. Inthis context, the geometric centre point of this circular or ellipsoidalcurvature does not lie on the geometric axis of symmetry of the rollerbody but rather is spaced apart from it.

This curved, in particular toroidal, surface has proven particularlysuitable in complex trials for reducing damage produced by the runningup of the end face against the rim running face.

The present invention is also aimed at a roller bearing with a racewayfor roller bodies which has at least one lateral rim for axially guidingthe roller bodies, wherein the rim has a rim running face which isturned toward the roller body, and a notch is provided in a cornerregion between the raceway and the rim running face. According to theinvention, the notch and the wall of the rim merge one into the otheressentially without an edge.

In other words, a tangent to an end point or end region of the notchextends essentially parallel to the rim running face. In contrast, thisparallelism does not occur in the prior art, in other words there is anedge. This edgeless transition means that the roller body and its endface cannot be damaged by the edge when they run up.

In a further preferred embodiment, the notch has at least in sections acircular-segment-shaped profile, wherein this circular-segment-shapedprofile has a radius of curvature which is between 0.5 mm and 2 mm, andpreferably between 1 mm and 1.5 mm. This notch serves, as stated above,as a grinding undercut which permits the raceway to be ground. Since theprofile between the notch and the wall is edgeless, it is not possibleto grind the rim running face.

The notch preferably has an end region facing the raceway of the bearingring, and in this end region said notch extends at an angle with respectto the raceway which is between 20° and 40°, preferably between 25° and37°, and particularly preferably between 30° and 34°.

The present invention is also aimed at a roller body, wherein accordingto the invention the roller body has at least one and preferably two endfaces which are curved at least in sections, in particular are curvedlogarithmically or in a toroidal shape.

This end face which is curved in particular in a toroidal shape ensuresthat the contact between the rim and the roller body is not punctiformor linear but rather over a surface. This contact over a surface permitsimproved lubrication of the roller bearing.

The roller body preferably has, in at least one end region, a lateralface which is curved in the axial direction of the roller body. In thisway it is also possible to improve the running up of the roller bodywith respect to the raceway. The lateral face is preferably curvedconvexly.

The present invention is also aimed at a roller bearing having a bearingring of the type described above, and at a roller bearing having atleast one roller body of the type described above.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of the disclosure. For a better understanding of the invention, itsoperating advantages, specific objects attained by its use, referenceshould be had to the drawings and descriptive matter in which there areillustrated and described preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a partial illustration of a bearing ring according to theprior art;

FIG. 2 shows a partial illustration of a bearing ring according to theinvention;

FIG. 3 shows an illustration of the production method for a bearing ringaccording to the invention;

FIG. 4 shows a partial illustration of a bearing ring according to theprior art with a roller body;

FIG. 5 shows an enlarged partial illustration of a bearing ringaccording to the invention with a roller body;

FIG. 6 shows an illustration of a bearing ring with a roller body;

FIG. 7 shows an enlarged illustration of a bearing ring with a rollerbody according to the invention;

FIG. 8 shows an enlarged illustration of a roller bearing according tothe invention;

FIG. 9 shows a detailed illustration of a bearing ring with a rollerbody;

FIG. 10 shows a roller body; and

FIG. 11 shows a further embodiment of a roller body according to theinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a detail illustration of a bearing ring 2 manufacturedusing a method known from the prior art. The reference symbol 4 hererefers to a central region of the bearing ring and the reference symbol6 refers to a lateral rim. The rim running face 6 a of the rim is facinga roller body (not shown).

As mentioned at the beginning, in the method known from the prior artthe notch 7 or the grinding undercut is formed in the material beforethe hardening process. The material is hardened only after this. In thismethod it is also still necessary to grind the rim running face 6 a.Therefore, the notch 7, as shown in FIG. 1, is formed in an obliquedirection with respect to the rim 6 and the central region 4. As aresult, an edge 30 is produced in the rim running face 6 a in the priorart. This sharp edge 30 can have unfavorable effects on the start ofaxial movement, in particular of planar roller end faces.

FIG. 2 shows a bearing ring manufactured according to the inventivemethod. In this context, the material of the bearing ring is firstlyhardened and the end contour, in particular the end contour of the rimrunning face 6 a, is then produced by hard turning. In this case,subsequent grinding of the rim running face 6 a is not necessary, butonly the raceway 4 a of the central region 4 needs to be ground. In thiscase, the tool for producing the grinding undercut is introduced intothe notch 7 in the radial direction P1 of the bearing ring 2, avoidingan edge 30 being formed as in FIG. 1.

To be more precise, the hard turning of the rim face 6 a is finished bycomplying with a necessary mean value for the rim aperture in the regionbetween 90° and 92°, for example 90.5°, and in a final work step thegrinding undercut is formed in order to permit the raceway 4 a to beground.

The reference symbol 9 refers to an end region of the notch 7 facing theraceway 4 a. This end region runs in an axial direction at an angle ofapproximately 32° with respect to the raceway.

FIG. 3 illustrates the production of the notch 7 or of the grindingundercut in a method according to the invention. For this purpose, atool 13 is pushed into the bearing ring 2 in an essentially radialdirection (arrow P1) after the hard turning of the bearing ring. Thereference symbol 12 characterizes a groove body of the tool 13. Thereference symbol d denotes the grinding dimension, which is in thevicinity of 0.5 mm. The angle β between the edge 12 b of the groove body12 and the raceway 4 a is in a range between 30° and 35°.

The rim running face 6 a does not extend at an angle of precisely 90°with respect to the raceway 4 a but rather at a slightly larger angle.The angle γ between the edge 12 a of the groove body 12 and the rimrunning face 6 a is between 3° and 4°.

FIG. 4 is an illustration of a detail of a bearing ring according to theprior art with a roller body 5 which runs up against it. In thiscontext, the rim angle is not illustrated to scale here. It is apparentthat the roller body 5 can make contact with the edge 30 of the grindingundercut at the notch 7. Since the roller body moves with respect tothis sharp edge 30, the small damage which was mentioned at thebeginning can occur to the roller body and therefore accelerated wearthereof may occur. The reference symbol 11 refers to the end face of theroller body.

FIG. 5 shows a bearing ring with a roller body in which the bearing ringhas been manufactured with the methods according to the invention. It isapparent that in this case there is no edge 30 and therefore the rollerbody 5 is treated in a correspondingly gentler way.

FIG. 6 shows an illustration of a bearing ring 2 with a roller body 5.This concerns a hard-turned bearing ring also. The end face 11 of theroller body 5 has a central region 11 a which can be implemented inessentially any desired way since it does not run up against the rim 6.It is also conceivable for the central region 11 a of the end face 11 tohave a trough or the like. As a result of the special configuration ofthe edge regions 11 b of the end face 11 it is possible to ensure thatonly a single contact point occurs between the rim and the end face,which is explained in more detail below.

The contact point between the end face 11 of the roller body and the rimface 6 a is denoted by 8. The radius of curvature of the corner region15 of the roller body is between 0.5 mm and 4 mm, preferably between 1mm and 2 mm, and particularly preferably in the vicinity of 1.5 mm.

The reference sign L refers to the rotational axis or axis of symmetryof the roller body 5. The reference symbol 14 denotes a toroidal centerpoint line on which, given a toroidal curvature of the roller body, thegroove point 16 or center point for the toroidal curvature lies. Theline 14, and therefore the groove point for the toroidal curvature, ispreferably located at the level of the end face 17 of the rim 6.

FIG. 7 shows an enlarged illustration of the arrangement shown in FIG.6. Here, the reference symbol TV denotes the distance by which thetoroidal center point line 14 is displaced with respect to the axis L ofsymmetry. This means that in the embodiment shown in FIG. 7 thecurvature in the edge region 11 b of the end face 11 of the roller bodylies on a circle whose circle center point (which is equal to the groovepoint 16) lies in turn on the line 14. Here, the edge region 11 b is asingle curved region continuously curving in an axial direction awayfrom the central region 11 a.

The reference symbol LW_(max) refers to the maximum length of the rollerbody, and the reference symbol LW refers to the length of the rollerbody in the vicinity of the contact point 8 between the roller body andthe rim running face 6 a. This contact point 8 is at the distance BAfrom the raceway 4 a of the bearing ring 2. In the embodiment shownhere, the contact point 8 is approximately at the same distance, in theradial direction, from the end face 17 of the rim 6 and from the raceway4 a of the bearing ring.

FIG. 9 shows an enlarged illustration of a bearing ring according to theprior art with a roller body 5. Here, the illustration has been enlargedto different degrees in the x and y directions.

It is apparent that when the roller body according to the prior art isused, an edge 32 of the roller body runs up against the rim face 6 a ofthe rim. This running up of the edge also leads over time to an adverseeffect on the rim face. The notch 7 is not shown in FIG. 9.

As mentioned at the beginning, the present invention is based on theobject of increasing the service life of such roller bearings, and inparticular of improving the running up of the roller bodies against therims of the bearing ring or rings.

FIG. 8 shows a bearing ring 2 which is used with a roller body 5 whichis improved according to the invention. Here too, the illustration hasbeen enlarged to different degrees in the x and y directions.

This roller body does not have any sharp corner edges but rather hasrounded edge regions 11 b which are embodied in this case in the mannerof a torus. The grinding undercut or the notch is not shown in theillustration in FIG. 8. It is apparent that as a result of the toroidalembodiment of the edge region 11 b, sharp-edged contact does not occurbetween the rim running face 6 a and the end face 11 or the end faceregion 11 b of the end face 11. As a result, during operation it ispossible to avoid wear on the end face and therefore the roller body aswell as the rim running face 6 a. Ideally, in the embodiment shown inFIG. 8 essentially one contact face 8 is provided between the rollerbody and the rim running face 6 a.

FIG. 10 shows a roller body. It is apparent that the end face in thisembodiment is of essentially spherical shape. The center point of thissphere or spherical segment face is located on the rotational axis L oraxis L of symmetry of the roller body. The radius R of the sphericalconfiguration is between 300 mm and 800 mm, preferably between 500 mmand 700 mm, and particularly preferably between 570 mm and 620 mm.However, the selection of this radius also depends on other geometriesof the roller body, for example its length Lw and its diameter Dw. Inthe corner region 15, the roller body preferably has, as mentionedabove, a radius between 1 mm and 2 mm. The use of a roller body 5 in theembodiment shown in FIG. 10 requires a rim angle of aperture in thevicinity of 92°. The reference sign DW characterizes the diameter of theroller body.

FIG. 11 shows a further embodiment of the roller body according to theinvention. In contrast to the embodiment shown in FIG. 10, the end facein the embodiment shown in FIG. 11 is of toroidal design. This meansthat here the center point of the circular faces 11 b does not lie onthe axis L of symmetry but rather is offset with respect to it by apredefined distance a. This is illustrated by the circular line K forthe lower edge region 11 b. In the embodiment shown in FIG. 11, theradius of the curvatures is in the regions 11 b over the length L of theroller body.

In the point of intersection S between the toroidal center point line 14and the end face 11, the central region 11 a and the edge region 11 bmerge with one another without an edge.

The central region 11 a of the end face can also have a planar profilein this embodiment. From FIG. 11 it is apparent that the geometriclocation of all the center points of the respective circular lines K islocated itself on a circular ring around the axis of symmetry with theradius a.

The method according to the invention or the bearing componentsaccording to the invention result in a larger effective rim height andtherefore an improved running up of the roller end face onto the rimface since the sharp edge of the notch 7 is dispensed with, andtherefore this region can also be used for the running up of the rollerbody. Since the dressing, for example the grinding, takes place afterthe heat treatment, the cooling does not result in any distortion due toheat treatment of the individual bearing components.

Subsequent to this process, the lateral line and/or the roller end faceor the roller end faces can preferably be honed.

Since production can occur in a clamped region between tips, it is alsopossible to avoid run-out errors with the respectively produced orprocessed roller bodies, which may arise due to remounting.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the inventive principles, it will beunderstood that the invention may be embodied otherwise withoutdeparting from such principles.

We claim:
 1. A bearing assembly, comprising: a plurality of rollerbodies having an end face, the end face having a flat central region anda single curved region continuously curving in a single axial directionaway from a plane of the central region at each end of the centralregion; and a bearing ring having a raceway for the roller bodies and alateral rim extending radially from an end of the raceway, the lateralrim axially guiding the roller bodies and having a rim running faceopposing the roller bodies, and a corner region with a notch beingformed between the raceway and the rim running face such that the notchand the rim running face merge with one another essentially without anedge, wherein the end face of the rolling body is subjected to ahard-turning process, and the raceway is ground, wherein only the curvedregions of the roller bodies contact the rim running face at a singlepoint and the central region of the roller bodies does not contact therim running face.
 2. The bearing assembly as claimed in claim 1, whereinthe notch has a circular-segment-shaped profile at least in sections. 3.The bearing assembly as claimed in claim 2, wherein thecircular-segment-shaped profile has a radius of curvature between 0.5 mmand 2.0 mm.
 4. The bearing assembly as claimed in claim 1, wherein thenotch has an end region which extends at an angle with respect to theraceway between 20° and 40°.
 5. The bearing assembly as claimed in claim2, wherein the circular-segment-shaped profile has a radius of curvaturebetween 1.0 mm and 1.4 mm.
 6. The bearing assembly as claimed in claim1, wherein the notch has an end region which extends at an angle withrespect to the raceway between 25° and 37°.
 7. The bearing assembly asclaimed in claim 1, wherein the notch has an end region which extends atan angle with respect to the raceway between 30° and 34°.
 8. The bearingassembly as claimed in claim 1, wherein the end face is curvedlogarithmically or in a toroidal shape.